Pressure swing adsorption (PSA) is a known method for the separation of gases. A relatively recent review of diverse PSA cycles has been presented by D. Tondeur and P. C. Wankat, "Separation and Purification Methods", 14(2), 157-212 (1985). This review in its FIG. 2, page 160, illustrates schematically the usual four steps of a frequently used PSA cycle, namely the four steps of compression (i.e. pressurization), high pressure production (i.e. feed), decompression (i.e. blowdown), and low pressure purge, although PSA cycles, many commercialized, comprising as few as two to more than ten steps are known and discussed in this review.
Of interest is U.S. Pat. No. 4,264,340, S. Sircar et al., who teaches a vacuum swing adsorption (VSA) process, which provides purified oxygen and nitrogen by a VSA cycle including a rinse step. A U.S. Pat. No. 4,013,429, S. Sircar et al., also teaches another adsorption process for air fractionation to provide a high purity nitrogen product gas and an oxygen-enriched gas fraction, which process includes a nitrogen rinse step.